Not sure I have any advice because I still don't understand what Concierge was asking us for. Perhaps discretely ask a Concierge host when you board the ship.
To the comments above. Our state room was automatically charged $15.50/night/guest. We were on a 12 night cruise with 4 in our stateroom -- $744.
We received a separate form for the concierge tip that suggested $8/night/guest. We filled out the form and added (rounded up) $500 for concierge.
The concierge host called and said I didn't understand the form and was supposed to give them $8/night for each of the 7 concierge team members (=$8 x 12 nights x 7 concierge staff members). They came to our door with a new form for us to fill out. We rounded up and gave them $700. In addition, we gave the 2 concierge team members who bring the beverage cart around each night $100 cash because they were so entertaining.
It was a wonderful cruise, but to my earlier point, an uncomfortable ending. I hope they make it more clear on the expectation going forward.